1. Field of the Invention
The invention relates to one-dimensional nanowires comprising a metallic core and sheathed with a metal oxide, in particular a ceramic material, and branched nanostructures constructed from aforementioned sheathed nanowires, a method for producing them and their use.
2. Discussion of Background Information
In the context of general miniaturization, primarily in the field of electronic components, the properties of the materials used change the further one advances into the submicron range. Hitherto use has been made principally of nanoparticles having dimensions in the nanometer range in all three spatial directions (so-called 0-dimensional structures), and of thin layers having a dimension in the nanometer range in one spatial direction (so-called 2-dimensional structures).
Primarily as a result of the miniaturization of electronic components, but also as a result of the miniaturization in other fields, there is increasingly also a need for fibers or wires, branched wires, cables and networks thereof in the submicron range (so-called 1-dimensional structures).
Previous methods for producing such one-dimensional structures principally consist in using noble metal catalysts or using templates. Wu et al., J. Am. Chem. Soc., 2001: 123:3165-3166, describe, e.g. the production of Ge nanowires, wherein gold nanoclusters are used as catalysts. A template-controlled method is described e.g. by Martin, Science 1994; 266:1961-1966. What is disadvantageous about all these methods is that they require the use of foreign materials, such as catalysts or templates, which lead to contaminations of the corresponding structures.
An overview of nanowires and their production is found in Xia et al., Adv. Mater. 2003, 15, No. 5, pp. 353-389. The studies according to the prior art are often directed toward nanowires composed of one material. However, a combination of different properties is often required for use e.g. as miniature components. In general this can be achieved only by means of composite structures, that is to say structures constructed from a combination of two or more materials.